A known image reading device includes a flatbed-type image scanner and an automatic document feeder (ADF), which is disposed at a top of the flatbed-type image scanner.
The known image reading device includes two image sensors. When the image reading device is used as an ADF-type image scanner, the image reading device reads images on both sides of a document at substantially the same time.
More specifically, a first image sensor is used when the image reading device is used as the flatbed-type image scanner. When the device is operated a the ADF-type image scanner, the first image sensor is used to read an image on one side of a document while a second image sensor is used to read an image on the other side of the document.
The first image sensor is configured to stay at a position under a contact glass to read an image on the one side of the document that is being conveyed along an upper surface of the platen glass. The second image sensor is fixed at a position above the platen glass and is configured to read an image on the other side of the document that is being conveyed along the upper surface of the platen glass.